Yumenoshima is a man-made island in Koto Ward, Tokyo.
In fact, much of the land area of Koto Ward is reclaimed land. I have been told by many people that the image of Yumenoshima as a rubbish dumping site is very hard to erase. The island started its life in 1957 as, indeed, a waste dump. Then in October 1978, a 43-hectare park opened to the public, with a number of good quality sports facilities.
When I visited the park recently I was impressed by the groups of mature trees around the park, especially in front of the tropical greenhouse. Evergreens are the backbone of the park’s plantings, and from the high elevated Shin-Kiba railway station nearby it looks like a natural evergreen woodland.
Since the park is so close to the sea, the emphasis is on trees that will tolerate salt air. Notable is the evergreen oak Pasania edulis (mateba-shii); its leaves are leathery, 8-16 cm long and 3-6 cm wide, with a shiny, waxy coat on the upper surface to protect it. Other park trees include the evergreen camphor tree (kusunoki, Cinnamomum camphora) and the deciduous Chinese elm (aki-nire, Ulmus parvifolia) which despite its name is native to Japan.
The park also cultivates eight species of Australian gum (Eucalyptus) trees in the open air. In special greenhouses close to the main tropical house a further nine species of gum trees are cultivated as a food crop for the koala bears (Phascolarctos cinerus) in Tama Zoo.
Eucalyptus trees are the tallest flowering plants in the world; some species grow as tall as 90 meters in their native habitat, which is southeast Australia and Tasmania. Unfortunately the different species are not clearly labeled; nevertheless, you can still admire their bark and their long narrow leaves.
The big attraction though is the tropical greenhouse, opened in November 1988, with a triple glass dome 28 meters high, heated by excess heat from the nearby incinerator.
This is a real educational garden, a good place to start for those who wish to know more about the tropical rain forests (nettai-urin) of Iriomote Island in Okinawa Prefecture or the semitropical plants of the Ogasawara island group. The Ogasawara Islands (formerly called the Bonin Islands) are 1,000 km southeast of Tokyo in the Pacific Ocean. They were claimed by Japan in 1875 and in 1880 they were placed under the administration of Metropolitan Tokyo.
Step into the video room first for a 15-minute video on Iriomote and the Ogasawaras. The mangrove forests on Iriomote and other islands in the Okinawa archipelago are explained in detail, as well as scenes of the lifestyles of the people on these islands.
The greenhouse is divided into three sections. The “A” dome contains plants from tropical regions around the globe. In the pond you can see the large-leafed Amazon water lily (o-onibasu, Victoria amazonica), native to the Amazon jungle, and a small mangrove tree. I suppose no tropical greenhouse would be complete if it didn’t have a mangrove in the collection.
The mangrove, Yaeyama hirugi (Rhizophora mucronata), is native to tidal river marshes of tropical and semitropical areas of Okinawa, especially along the river Urauchi on Iriomote Island. A small tree, it has aerial roots, or pneumatophores (kikon), which come out of the main stem. Mangrove bark is high in tannin and is harvested for use in tanning leather.
The giant bamboo Dendrocalmus giganteus is very impressive. The huge stems have a girth of 18-30 cm and reach the roof in this glasshouse. In their native habitat of Assam in India, this giant bamboo grows to over 28 meters. The young shoots are purplish in color.
Tree ferns are a feature of Okinawa rain forests. Cyathea lepifera (hikage hego) is the tallest Japanese tree fern; a fast-growing plant, it is native to Amami Oshima.
The large and very strange Java stagshorn fern (Platycerium willinckii) is a lovely sight, its leaflike fronds 90 cm tall. The world’s tropical areas support 18 species of stagshorn fern; these ferns are epiphytic (chakusei), using tree trunks for support. The Java stagshorn fern at Yumenoshima is the largest and the best I have ever seen.
The path leads under a waterfall to a small tunnel which is covered by a giant “Swiss-cheese plant” (monsutera, Monstera deliciosa). This is also an epiphytic climber, native to tropical Mexico and Panama. The natural holes in the leaves give the plant its English name.
Once you have passed through the tunnel you are in the center or B dome, the tallest and the most spectacular, with an excellent collection of palm trees from around the world. The year-round high temperature and high humidity give them ideal growing conditions. The temperature was 22 C when I visited the greenhouse in January.
There is even a tropical thatched house to contribute to the steamy jungle feeling. The roof is thatched with leaves of the water palm (nippa-yashi, Nipa fruticans), a native of tropical India.
The grandest of all the palms is the Cuban royal palm (daio-yashi, Roystonea regia). In its native Cuba this palm grows to 25 meters, so the trees here in this house are full size. The trunk is grayish-white in color and very smooth. Nearby is the alexandra palm (yusura-yashi, Archontophoenix alexandrae), from northeast Australia, where it grows to 25 meters; its trunk is characteristically swollen at the base.
The Yaeyama yashi (Satakentia liukiuensis) is native to Okinawa. A climbing plant called habu-kazura (Epipremnum decursiva) adheres to its trunk, deriving its Japanese name from Okinawa’s much-feared poisonous snake, the habu (Trimerusurus flavoviridis).
The C dome features the plants of the Ogasawara Islands, some of them very strange indeed. Take for example the screw pines (tako-no-ki, Pandanus boninensis) — the Japanese name means “octopus tree!” There are over 600 different species of screw pines, all native to Southeast Asia, Malaysia and Australia. Like the mangroves, they have aerial roots coming out of the main stem in great numbers, hence the Japanese popular name. The fruit looks somewhat like a pineapple. The long narrow leathery leaves have razor-sharp edges.
The travelers palm (ogibasho, Ravenala madagascariensis) grows only in Madagascar. It is not a real tree, but a giant herbaceous plant with a stem made of dead-leaf bases, that grows to a height of 10, 20 or even 30 meters in its native habitat. The leaves are up to 5 meters long, and come out of the stem at right angles, so from a distance it looks like a giant fan.
Leaving the greenhouse, you enter the information gallery. Here videos offer you more information on tropical rain forests of the world. I hope you have been paying attention. There will be a quiz — in Japanese.